The hypothesis to be examined is that ketones are involved in the regulation of suckling in the rat pup. It derives from the evidence that up to 18 days of age, but not thereafter, ketones comprise a major energy substrate in the brain, and from the authors' recent work indicating that glucoprivation will not increase ingestion before 18 days of age. The experiments proposed will examine the effects of both reducing and increasing the availability of ketones on ingestion in the pup. Reductions in ketone availability will be effected by maintaining the dams of the experimental pups on a high fat diet, and treating the pups with methyl palmoxirate. These treatments reduce the availability of medium and long chain fatty acids required for ketogenesis. An adjunctive treatment with the glucose anti-metabolite 5-thioglucose will be administered to exascerbate energy privation and to examine the effect on ingestion of these agents across the transition from a ketone to a glucose based energy metabolism. Increases in ketone concentrations in the brain will be effected by intracerebroventricular injections of ketones. The efficacy of the treatments will be monitored by analysis of blood metabolites. Feeding responses will be examined away from the dam (by intraoral infusion of milk) and while the pup is suckling on the dam. These experiments will reveal whether ketones, a unique and major energy substrate for the suckling brain, play a role in the regulation of intake in the pup, and whether this role is specific to suckling, or general to nutrient intake and energy balance.